AMYLASE IN PECTEN-MAXIMUS (MOLLUSCA, BIVALVES) - PROTEIN AND CDNA CHARACTERIZATION - QUANTIFICATION OF THE EXPRESSION IN THE DIGESTIVE GLAND

The digestive enzyme alpha-amylase in Pecten maximus has been purified from the digestive gland, where it is present as two isoforms. In ord er to gain information on its structure and regulation, a digestive gl and cDNA library, constructed in lambda phage Zap II (Stratagene, La J olla, Calif., U.S.A.), was screened with a shrimp alpha-amylase cDNA p robe. Only 0.02% of the clones were positive, and the longest clone, h aving a size of 1700 bp and identical to that of the mRNA, was fully s equenced. It contains the complete cDNA coding frame for one of the am ylase isoforms of P. maximus. The deduced protein sequence is 508 amin o acids long, with a putative 18 amino acid, highly hydrophobic signal peptide and a mature enzyme of 489 residues. The molecular weight cor responds to 54,500 Da and the calculated isoelectric point is 6.76. Lo cation of conserved sequences confirms the high level of similarity wi th the other members of the family (EMBL Accession No. X99729).